Current technologies for highly portable power systems can store energy in the form of un-reacted electrochemical components with potentials of a few electron volts per reaction. This limits the specific energy of such systems to a few megajoules per kilogram. Nuclear battery concepts can achieve a specific energy increase over electrochemical concepts but at the cost of ionizing radiation dangers, poor specific power by comparison to electrochemical solutions, and posing proliferation risks.
Techniques to store entropy rather than energy and to use entropy to improve energy harvesting from low quality sources have been proposed. For example, U.S. Pat. Pub. No. 2011/0252798, which is incorporated by reference in its entirety herein, describes systems and methods that use stored entropy to harvest energy using a “quantum heat engine” (QHE).
Quantum heat engines produce work using quantum matter as their working substance. A variety of theoretical QHEs have been proposed, such as those described in Scully et al., “Using Quantum Erasure To Exorcize Maxwell's Demon: I. Concepts And Context”, Physica E 29 (2005) 29-39; and Rostovtsev, Yuri, et al., “Using Quantum Erasure To Exorcise Maxwell's Demon: II. Analysis”, Physica E 29 (2005) 40-46; Ramandeep S. Johal, “Quantum Heat Engines And Nonequilibrium Temperature”, Quant. Ph., 4394v1, September 2009; and Ye Yeo et al., “Quantum Heat Engines And Information”, Quant. Ph., 2480v1, August 2007, each of which is incorporated herein by reference in its entirety. These theoretical quantum heat engines, however, can be impractical or impossible to reduce to practice and can be limited to use with either interacting or non-interacting working fluids and can be limited to use with either classical thermal reservoirs or quantum reservoirs.
Accordingly, there is a continued desire for improved quantum information engines and quantum heat engines that can take advantage of quantum coherence and correlations for efficient work harvesting.